Process for preparing detergent granules from trimetaphosphate



United States Patent 3,345,297 PROCESS FOR PREPARING DETERGENT GRANULES FROM TRIMETAPHOSPHATE Larry E. Meyer and Richard D. Walker, Cincinnati, Ohio,

assignors to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio No Drawing. Filed Dec. 6, 1965, Ser. No. 511,982

9 Claims. (Cl. 252-137) This invention relatesto an improved process for preparing detergent granules by the trimetaphosphate foamed process.

The first step in the trimetaphosphate foamed process is the formation of a precursor slurry. This slurry usually contains an alkali metal trirnetaphosphate salt, water,

(Tn'sodium'trlmetaphosphate) The resultant sodium tripolyphosphate combines with free water in the slurry to form the hexahydrate. As the reaction between the base material, e.g., NaOH, and the trimetaphosphate proceeds, the heat of conversion of the trimetaphosphate to tripolyphosphate converts free Waterin the slurry into steam. As the steam forms and escapes, it transforms the detergent slurry into a fairly light density foam. Thus, free water in the slurry is consumed as steamv or water of hydration in the tripolyphosphate hydrate. The foamed product is obtained in .a semiparticulate mass.

After a subsequent drying step, the product, which is an excellent detergent, can be sized, screened and-packed; The trimetaphosphate foamed process has several processing advantages; it also has some serious deficiencies. One of these deficiencies is the relatively high viscosity of the precursor slurry. At ordinary and commercially feasible usage levels of water, substantial effort and mix-j ing time must be expended in order to obtain a homo-j geneous precursor slurry. The high viscosity of the slurry presents special problems at that stage in theprocess at which the strong base is being added. If the slurry is too viscous, the base can be prevented from reacting with ,all of the trimetaphosph-ate and, therefore, that trimetaphosphate which is not contacted by the base will not be converted to tripolyphosphate. In other words, the base, e.g., sodium hydroxide, must be mixed evenly throughout theslurry to get a complete reaction and maximum conversion of the trimetaphosphate to tripolyphosphate.

I Another deficiency of the trimetaphosphate process is;

3,345,297 Patented Oct. 3, 1967 ice that air can become entrained in -a highly viscous detergent slurry. The entrained air can cause the slurry density to decrease and, thus, the density of the finished product to decrease. At times it is desired to produce a high density detergent product. If entrapped air is not released-from the slurry, the finished product is frangible and readily degrades into a powder form. Although entrained air can be removed mechanically, this is an expensive and timeconsuming process. Accordingly, it is an object of this invention to provid a process for reducing the viscosity of the precursor slurry without increasing the Water content of the slurry. It is.

a further objectof this invention to provide {a process for for efficiently mixing a trimetaphosphate slurry. Another object of this invention is to provide a process wherein substantially all of the trimetaphosphate' is converted into stood, however, that the detailed description and specific examples, While indicating preferred embodiments of the invention, are given by Way of illustration only since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.

It has now been discovered that the foregoing objects of the present invention are obtained by a process comprising the steps of:

(1) Forming a precursor slurry by mixing together, by Weight based on the final slurry, from about 20% to about 45% of water, from about 0.2% to about 12% of a water-soluble salt of nitrilotriacetic acid, and from about 20% to about 60% of an alkali-metal trirnetaphosphate;

(2) Adjusting the temperature of the precursor slurry between about F. and about 212 F.;

(3) Admixin-g into the continuously stirred precursor slurry from about 1.5 to about 3.0 moles of an alkali metal hydroxide per mole of alkali metal trimetaphosphate to form the final slurry,said alkali metal hydroxide reacting with said trimetaphosphate and converting it to an alkali metal tripolyphosphate with a resulting evolution of a substantial amount of steam from the slurry, the temperature of the slurry being maintained below about The term, final slurry, as used herein is the slurry a y it exists when the alkali metal hydroxide is added and before water is lost as steam (on an actual or theoretical basis). v

, In the first step of the process of this invention, a precursor slurry is formed which comprises water, a water-'solublesalt of nitrilotriacetic acid, and an alkali metal trimetaphos-phate, e. g., sodium or potassium trimetaphosphate.

Water is essential to the precursor slurry to initially lend fluid properties thereto. The precursor slurry can comprise from about 20% to about 45% by weight water, based on the final slurry. When less than 20% water is utilized in this step of the process, the slurry is generally too thick and viscous to be properly processed. When more than 45% water is utilized, the cost of drying the final product becomes prohibitive. In a preferred embodiment of this invention, the precursor slurry comprises from about 30% to about 38% by weight water, based on the final slurry.

The essence of the present invention and the principal departure from prior art processes is the addition to the precursor slurry of a water-soluble salt of nitrilotriacetic acid which has the general formula CHZCOOH NCHzC'OOH CHzCOOH wherein a suitable cation is substituted for the acidic hydrogens in the above formula, the cation being sodium, potassium, other alkali metals, or ammonium or substituted ammonium radicals, e.g., triethanolamine. The trisodium salt of nitrilotriacetic acid is the preferred Watersoluble salt of nitrilotn'acetic acid for use in this invention.

Nitri-lotriacetic acid may be utilized in place of the water-soluble salts described above. Upon the later addition of the alkali metal hydroxide to the deter-gent slurry, an alkali metal nitrilotriacetic acid salt will be formed in situ in the slurry.

The water-soluble salts of nitrilotriacetic acid are employed in the precursor slurry from about 0.2% to 12% by weight, based on the final slurry. In a preferred embodiment of this invention, the precursor slurry comprises from about 2% to about 9% by weight of these salts, based on the final slurry.

The inclusion of the nitrilotriacetate salts in the precursor slurry provides totally surprising and unexpected results. While not wishing to be bound by any particular theory, it is believed that the water-soluble salts of nitrilotriacetic acid cause a phase transformation in the precursor slurry, e.g., a continuous phase and a discontinuous phase. The continuous phase is comprised primarily of water and is, therefore, very fluid. The discontinuous phase, on the other hand, is comprised of discrete globules of the various solids in the slurry, including trimetaphosphate. The formation of these separate phases results in an apparent decrease in viscosity of the slurry as there is little cohesion between the discrete globules of the discontinuous phase.

The viscosity decrease afforded by addition of watersoluble salts of nitrilotriacetic acid to the precursor slurry facilitates more efficient mixing procedures at the usual usage levels of water. This decrease of viscosity in the precursor slurry is especially valuable when the alkali metal hydroxide is added to the slurry. Because of the viscosity decrease and the two-phase system, the alkali metal hydroxide can more easily contact and react with the trimetapohsphate and, therefore, substantially all of the trimetaphosphate is converted into tripolyphosphate.

The decreased viscosity due to the addition of watersoluble salts of nitrilotriacetic acid to the precursor slurry also facilitates deareation of the slurry and, thereby, increases the density of the slurry and, likewise, the density of the final product. While again not wishing to be bound by any particular theory, it is believed that the abovereferred-to phase separation facilitates the escape of the entrapped air. It is believed that the entrapped air can more easily escape through the less viscous continuous phase. This improvement is an especially valuable one because the expensive process and machinery required for mechanical deareation can be eliminated.

Additionally, the detergent granules made according to this process are less frangible, are tougher, and are highly desirable for making detergent tablets of compressed granules. Frangibility, as used herein, is a measure of the tendency of alkali metal tripolyphosphate granular particles to break into smaller particles during handling and processing.

The water-soluble salt of nitrilotriacetic acid, in addition to its main function in this process of reducing the viscosity of the precursor slurry and deareating the precursor -slurry, also exhibits synergistic builder action in the final detergent product when combined with alkali metal tripolyphosphate salts.

Such synergistic builder action described above is more 4 fully explained in a copending application by Burton H. Gedge, Ser. 498,908, filed Oct. 11, 1965.

It has been found to be highly advantageous to add the water-soluble salts of nitrilotriacetic acid to the precursor slurry before the trimetaphosphate salts are added. The most beneficient results in terms of viscosity decreases in the slurry and increased mixing efliciency are attained in this manner, and thus it represents a preferred embodiment of the present invention.

The other essential ingredient of the precursor slurry is an alkali metal trimetaphosphate (TMP). These salts, such as trisodium trimetaphosphate and tripotassium trimetaphosphate, have no buffering or sequestering powers per se, but they do possess the important property that when these salts are in the presence of hydroxyl ions in a slurry or solution, a tripolyphosphate salt is rapidly formed therefrom. The heat of conversion for this exo-- thermic reaction is about 27.4 kilocalories per mole of trimetaphosphate. This heat is sufficient to vaporize some of the free water in the slurry into steam. The escaping steam then forms the slurry into a light density foam.

In order to obtain good foaming action, the precursor slurry should contain at least about 20% by weight (based on the final slurry) of an alkali metal trimetaphosphate, preferably trisodium trimetaphosphate. The uppermost feasible limitation for the addition of alkali metal trimetaphosphate is about 60% by weight, based on the final slurry.

Although not essential to the process of this invention, the detergent slurry contemplated in this invention can additionally contain detergent substances such as soap, anionic synthetic non-soap detergents, nonionic synthetic detergents, ampholytic synthetic detergents, zwitterionic synthetic detergents and mixtures thereof. The addition of these detergent substances forms no limitation on this invention but is intended to be includable Within the terms of claims calling for the formation of a precursor slurry. Preferably, such detergents are employed in the precursor slurry in an amount by weight (based on the final detergent slurry) ranging from about 0% to about 30%, preferably 5% to 20%.

Examples of suitable soaps are the sodium, potassium and alkylolammonium salts of higher fatty acids (C -C Particularly useful are the sodium and potassium salts'of the mixtures of fatty acids derived from coconut oil and tallow, i.e., sodium or potassium tallow and coconut soap.

The other suitable detergent substances are outlined more at length as follows:

(a) Anionic synthetic non-soap detergents can be broadly described as the water-soluble salts, particularly the alkali metal salts, of organic sulfuric reaction products having in their molecular structure an alkyl radical containing from about 8 to about 22 carbon atoms and a radical selected from the group consisting of sulfonic acid and sulfuric acid ester radicals. (Included in the term alkyl is the alkyl portion of higher acyl radicals.) Important examples of the synthetic detergents which form a part of the preferred compositions of the present invention are the sodium or potassium alkyl sulfates, especially those obtained by sulfating the higher alcohols (C -C carbon atoms) produced by reducing the glycerides of tallow or coconut oil; sodium or potassium alkyl benzene sulfonates, in which the alkyl group contains from about 9 'to about 15 carbon atoms, including those of the types described in United States Letters Patents Nos. 2,220,099 and 2,477,383 (the alkyl radical can be a straight or branched aliphatic chain); sodium alkyl glyceryl ether sulfonates, especially those ethers of the higher alcohols derived from tallow andcoconut oil; sodium coconut oil fatty acid monoglyceride sulfates and sulfonates; sodium or potassium salts of sulfuric acid esters of the reaction production of one mole of a higher fatty alcohol (e.g., tallow or coconut oil alcohols) and about 1 to 6 moles of ethylene oxide; sodium or potassium salts of alkyl phenol ethylene oxide ether sulfate with about 1 to about units of ethylene oxide per molecule and in which the alkyl radicals contain from 8 to about 12 carbon atoms; the reaction product of fatty acids esterified with isethionic acid and neutralized with sodium hydroxide where, for example, the fatty acids are derived from coconut oil; sodium or potassium salts of fatty acid amide of a methyl tauride in which the fatty acids, for example, are drived from coconut oilg and others known in the art, a number being specifically set forth in United States Letters Patents Nos. 2,486,921, 2,486,922 and 2,396,278. Another anionic detergent suitable for use in this invention is described in the detergent which comprises by weight from about 30% to about 70% of Component A, from about 20% to about 70% of Component B, and from about 2% to about of Component C, wherein:

(I) Said Component A is a quaternary mixture of double-bond positional isomers of water-soluble salts of alkene-l-sulfonic acids containing from about 10 to about 24 carbon atoms, said mixture of positional isomers including by Weight about 10% to about 25% of an alphabeta unsaturated isomer, about 30% to about 70% of a beta-gamma unsaturated isomer, about 5% to about 25 of a" gamma-delta unsaturated isomer, and about 5% to about 10% of a delta-epsilon unsaturated isomer;

(2) Said Component B is a mixture of water-soluble salts of bifunctionally-substituted sulfur-containing saturated aliphatic compounds containing from about 10 to about 24 carbon atoms, the functional units beinghydroxy and sulfonate radicals with the sulfonate radical always being on the terminal carbon and the hydroxyl radical being attached to a carbon atom at least two carbon atoms removed from the terminal carbon atoms; and

(3) Said Component C is a mixture comprising from about 30-95% water-soluble salts of alkene disulfonates containing from about 10 to about 24 atoms, and from about 5% to about 70% water-soluble salts of hydroxy disulfonates containing from about 10 to about 24 carbon atoms, said alkene disulfonates containing a sulfonate group attached to a. terminal carbon atom and a second sulfonate group attached to an internal carbon atom not more than about six carbon atoms removed from said terminal carbon atom, the alkene double bond being distributed between the terminal carbon atom and about the seventh carbon, said hydroxy disulfonates being saturated aliphatic compounds having a sulfonate radical liquid character of the product is retained up to the point where polyoxyethylene content is about 50% of the total weight of the condensation product.

Other suitable nonionic syntehtic detergents include:

(1) The polyethylene oxide condensates of alkyl phenols, e.g., the condensation products of alkyl phenols having an alkyl group containing from about 6 to 12 carbon atoms in either a straight chain or branched chain configuration, with ethylene oxide, the said ethylene oxide being present in amounts equal to 5 to 25 moles of ethylene oxide per mole of alkyl phenol. The alkyl substituent in such compounds may be derived from polymerized propylene, diisobutylene, octene, or nonene, for example.

'(2) Those nonionic synthetic detergents derived from the condensation of ethylene oxide with the product resulting from the reaction of propylene oxide and ethylene diamine. For example, compounds containing from about 40% to about 80% polyoxyethylene by weight and having attached to a terminal carbon, a second sulfonate group attached to an internal carbon atom not more than about six carbon atoms removed from said terminal carbon atom, and a hydroxy group attached to a carbon atom which is not more than about four carbon atoms removed from the site of attachment of said second sulfonate 1 group (hereinafter referred to as olefin sulfonate).

(b) Nonionic synthetic detergents can be broadly defined as compounds produced by the condensation of alkylene oxide groups (hydrophilic in nature) with an organic hydrophobic compound, which may be aliphatic or alkyl aromatic in nature. The length of the hydrophilic or polyoxyalkylene radical which is condensed with any particular hydrophobic group can be readily adjusted to yield a water-soluble compound having the desired degree of balance between hydrophilic and hydrophobic elements.

As an example, a class of nonionic synthetic detergents is made available on the market under the trade name of Pluronic. These compounds are formed by condensing ethylene oxide with an hydrophobic base formed by the condensation-of propylene oxide with propylene glycol. The hydrophobic portion of the molecule which, of course, exhibits water insolubility, has a molecular weight of from about 1500 to 1800. The addition of polyoxethylene radicals to this hydrophobic portion tends to increase the water solubility of the molecule as a whole and the a molecular weight of from about 5,000 to about 11,000 resulting from the reaction of ethylene oxide groups with a hydrophobic base constiuted of the reaction product of ethylene diamine and excess propylene oxide, said base having a molecular weight of the order of 2,500 to 3,000, are satisfactory.

(3) The condensation product of alpihatic alcohols having from 8 to 22 carbon atoms, in either straight chain or branched chain configuration, with ethylene oxide, e.g., a coconut alcohol-ethylene oxide condensate having from 5 to 30 moles of ethylene oxide per mole of coconut alcohol, the coconut alcohol fraction having from 10 to 14 carbon atoms.

(4) Long chain tertiary amine oxides corresponding to the following general formula, R R R N O, wherein R is an alkyl radical of from about 8 to about 18 carbon atoms, and R and R are each methyl or ethyl radicals The arrow in the formula is a conventional representation of a semi-polar bond. Examples of amine oxides suitable for use in this invention include dimethyldodecyl amine oxide dimethyloctylamine oxide, dimethyldecylamine oxide, dimethyltetradecylamine oxide, dimethylhexadecylamine oxide.

(5) Long chain tertiary phosphine oxides corresponding to the following general formula RRRP O wherein R is an alkyl, alkenyl or monohydroyalkyl radicalranging from 10 to 18 carbon atoms in chain length and R and R" are each alkyl or monohydroxyalkyl groups containing from 1 to 3 carbon atoms. The arrow in the formula is a conventional representation of a semi-polar bond. Examples of suitable phosphine oxides are: dodecyldimethylphosphine oxide, tetradecyldimethylphosphine oxide, tetradecylmethylethylphosphine oxide, cetyldimethylphosphine oxide, stearyldimethylphosphine oxide, cetylethylpropylphosphine oxide, dodecyldiethylphosphine oxide, tetradecylidethylphosphine oxide, dodecyldipropylphosphine oxide, dodecyldi (hydroxymethyl) phosphine oxide, dodecyldi (2-hydroxyethyl) phosphine oxide, tetradecylmethyl-Z-hydroxypropyl phosphine oxide, oleyldimethylphosphine oxide, and 2-hydroxydodecyldimethylphosphine oxide.

. (c) Ampholytic synthetic detergents can be broadly described as derivatives of aliphatic secondary and tertiary amines, in which the aliphatic radical may be straight chain or branched and wherein one of the aliphatic substituents contains from about 8 to 18 carbon atoms and one contains an'anionic water solubilizing group, e.g., carboxy, sulfo, sulfato, phosphato, or phosphono. Examples of compounds falling within this definition are sodium-3-dodecylaminopropionate and sodium-3 -dodecylaminopropane sulfonate.

(d) Zwitterionic synthetic detergents can be broadly described as derivatives of aliphatic quaternary ammonium, phosphonium, and sulfonium compounds, in which the aliphatic radical may be straight chain or branched, and wherein one of the aliphatic substituents contains from about 8 to 18 carbon atoms and one contains an anionic water solubilizing group, e.g., carboxy, sulfo, sulfato, phosphato, or phosphono. Examples of compounds falling within this definition are 3-(N,N-dimethyl- N-hexadecylammonio) propane-l-sulfonate and 3-(N,N- dimethyl-N-hexadecylammonio) 2 hydroxy propane-1- sulfonate which are especially preferred for their excellent cool water detergency characteristics.

The soap and non-soap anionic, nonionic, ampholytic and zwitterionic detergent surfactants mentioned above can be used singly or in combination in the practice of the present invention. The above examples are merely specific illustrations of the numerous detergents which can find application within the scope of this invention. Other surfactants within the prescribed classes can also be used.

It will be understood by the worker skilled in the art that detergent slurries and the detergent compositions made therefrom, including the slurries of this invention, can ordinarily contain various other ingredients for special purposes. Thus, the detergent slurries of this invention can contain, in addition to the aforementioned detergent compounds, suds builders, suds depressants, anticorrosion agents, anti-redeposition agents, bacteriocides, dyes, fluorescers, perfumes, sodium sulfate and the like. Again, these detergent ingredients form no limitation on the invention but are intended merely to be within the terms of claims calling for formation of a precursor slurry.

The temperature of the precursor slurry should be from about 140 F. to about 212 F. At temperatures below 140 F., the trimetaphosphate conversion proceeds so slowly that the slurry is not foamed into a light density cake. At these low temperatures, trimetaphosphate is converted to tripolyphosphate salts but the reaction product is not particulate enough for use as detergent granules. Above 212 F., the physical act of mixing the alkali metal hydroxide into the precursor slurry is severely handicapped because the foaming action takes place very quickly after the addition of the alkali metal hydroxide. It is preferred in the process of this invention to maintain the precursor slurry at a tempeature of from about 165 F. to about 185 F. An alkali metal hydroxide is then added to the precursor slurry with continued stirring to insure thorough mixing of the hydroxide throughout the slurry. Either potassium or sodium hydroxide is generally used in this process. Sodium hydroxide is the preferred basic reactant for use in this invention.

The complete conversion of the trimetaphosphate salt to the tripolyphosphate salt theoretically requires two moles of alkali metal hydroxide per mole of the trimetaphosphate. Consequently, it is preferred that about that amount be added to the precursor slurry. However, satisfactory results are obtained with from about 1.5 to about 3.0 moles of alkali metal hydroxide per mole of trimetaphosphate salt. It is preferred that the alkali metal hydroxide be added in an aqueous solution to the precursor slurry to facilitate solubilizing of that strong base in the slurry. Any water in such an aqueous solution should be included as part of the permissible amounts set forth previously for the Water content based on the final slurry. It is further preferred that the aqueous solution containing the alkali metal hydroxide contain from about 20% to about 50% by weight of the alkali metal hydroxide. At these concentrations, a clear solution can be maintained at room temperature.

Immediately on addition of the alkali metal hydroxide to the slurry, the conversion from trimetaphosphate to tripolyphosphate begins. This reaction is highly exothermic and the heat of conversion is utilized to vaporize free water in the slurry. The vaporized water, i.e., steam, foams the slurry up to several times its original volume as the conversion proceeds. As the steam escapes from the slurry, it leaves behind a porous detergent mass.

The complete conversion reaction should take place at temperatures below about 275 F. If higher temperatures are utilized, the newly formed alkali metal tripolyphosphates will undergo hydrolytic degradation to the orthophosphates and pyrophosphates.

As the alkali metal tripolyphosphate forms, it hydrates, thus removing additional free water from the slurry. A further drying step may be required to obtain the desired solid, particulate composition containing an alkali metal tripolyphosphate. This drying step can be accomplished by various means well known in the art. Preferably, the final product should contain from about 12% to about 22% moisture (this includes both free water and water of hydration).

It is usually desirable to then size, screen and package the product produced by the process of this invention. The product can also be utilized to make detergent tablets.

The following specific examples are given in order to further explain and illustrate this invention. They are not intended to limit the scope in any way.

Example 1 The following components were mixed in a stainless steel, sigma blade mixer in the order indicated.

TAE is the condensation product of one mole of tallow alcohol and 11 moles of ethylene oxide. NTA-H O is trisodium nitrilotriacetate monohydrate. The sodium silicate has an SiO :Na O ratio of 1.6 to 1 and is an aqueous solution. Sodium hydroxide is, likewise, added in an aqueous solution. Sodium toluene sulfonate is a well known hydrotrope.

A precursor slurry was prepared from the first six listed components shown above. Water and TAE were first admixed in the sigma blade mixer. When the NTA-H O was added to the mixture of TAE and water, a graining effect, i.e., separation into a continuous and a discontinuous phase, was apparently induced. These phases were only barely discernible with the naked eye. The slurry retained this grained effect throughout the addition of the sodium toluene sulfonate, the sodium trimetaphosphate, and the sodium silicate. The precursor slurry was fluid and the various components were easily admixed even though only about 25% of the precursor slurry was water. The temperature of the precursor slurry was maintained at F.

When the sodium hydroxide soultion was added to the stirred precursor slurry, it was easily and homogeneously admixed therein. Immediately on addition of the alkali metal hydroxide to the slurry, the conversion from trimetaphosphate to tripolyphosphate began. The heat of conversion from this reaction was utilized to vaporize free water in the slurry. This vaporized water, i.e., steam, caused the slurry to foam up to several times its original volume. As the steam escaped, it left behind a porous detergent mass containing sodium tripolyphosphate hexahydrate. The temperature during this reaction was maintained in a range of from 220 F. to 230 F., and in no instance was allowed to exceed 275 F.

The sodium trimetaphosphate was nearly entirely converted to sodium tripolyphosphate with very little degradation of the tripolyphosphate to orthophosphates and pyrophosphates. The resulting solid particulate composition was comprised of particulate detergent granules.

It was apparent that the NTA-H O had deareated the precursor slurry. No mechanical deareation was required in order to obtain both a dense precursor slurry and tough, dense detergent granules which 'were less frangible than similar granules which did not contain NTA-H O.

In this example, several substitutions can be made without materially affecting the process of this invention or the productproduced thereby. Any of the hereinbefore enumerated water-soluble salts of nitrilotriacetic acid, e.g., the tripotassium salt, may be substituted for the trisodium salt; potassium hydroxide or other alkali metal hydroxide may be substituted for sodium hydroxide. Other alkali metal trimetaphosphates may be substituted for sodium trimetaphosphate, such as tripotassium trimetaphosphate. Also, other synthetic detergents may be utilized in this process, e.g., C C olefin sodium sulfonates or sodium linear C C alkyl benzene sulfonates. These synthetic detergents can be selected from any of the classes 'hereinbefore enumerated.

Example 2 The following components were mixed in a stainless steel, sigma blade mixer in the order indicated.

See Example 1 for more completedefinltion.

The TAB polypropylene glycol and sodium toluene sulfonate were combined in a homogeneous mixture. The addition of NTA-H O produced the graining elfect described in Example 1. The slurry retained this grained effect throughout the subsequent addition-of the sodium trimetaphosphate and sodiumsilicate. The precursor slurry was fluid and the various components were easily admixed. The temperature of the precursor slurry was maintained at 165 F.

Again, the sodium hydroxide was easily mixedintothe stirred precursor slurry. The foaming reaction-took place as described in Example I. The temperature ofthe reaction mass was maintained at from 210 F. to 230 F. during the reaction. The sodium trimetaphosphate was substantially completely converted to sodium tripolyphosphate. Again, the deaeration effect of the NTA-I-l o was substantially the same as related in Example 1.

The product was particulate and homogeneous. It was easily granulated and became crisp and tough in a short time. The composition of the final product, in parts by weight, was: parts TAE 7 parts anhydrous trisodium nitrilotriacetate, 1 part polypropylene glycol, 1 part sodium toluene sulfonate, 8.2 parts silicate solids and 52.2 parts sodium tripolyphosphate hexahydrate. These granules were then pressed into tablets which were strong, easy-dissolving and elfective detergents.

Example 3 Components Parts by Order of Weight Addition 27. 5 1 14. 6 2 8. 2 3 fa 15. 1 4 Sodium Trimetaphosphate 27. 7 5 TAEm" 7.0 6 Sodium Metasilicate 12. 4 7 Sodium Hydroxide 8. 0 8

*See Example 1 for more complete definition. The anionic paste comprised 60.0% water, 15.5% sodium :sulfate and 245% linear sodium alkyl benzene sulfonate wherein the alkyl group is a mixture of 10-18 carbon atom alkyls. The metasilicate was a free-flowing, granular product having an SiO :Na O ratio of about 1:1. Y

'The precursor slurry was easily mixed and was fluid and homogeneous. The trisodium nitrilotriacetic acid effectively deaerated the precursor slurry. The sodium hy droxide solution was easily admixed into the precursor slurry which was being maintained at a temperature of F. About 45 seconds after the addition of the sodium hydroxide solution, the slurry began to foam as described in Example 1. The temperature of the reaction mass was maintained below 275 F. After 2 minutes, the foaming reaction was completed. The detergent product felt dry and was particulate.

The product was further dried in a rotary drum with room temperature air and then screened. The product was pressed into detergent tablets. The granules were tougher and less frangible than granules which did not contain the trisodium nitrilotriacetate.

Example 4 v .The following components were mixed in a stainless steel, sigma blade mixer in the order indicated.

' See Example 3 for more complete definition.

b See Example 1 for more complete definition. I

The trisodium nitrilotriacetate was added after the anionic paste was charged into the mixer. Throughout the subsequent addition, of components, the mixture was smooth, fluid and easily mixed. The precursor slurry was continuously deaerated by the trisodium nitrilotriacetate while being maintained at a temperature of F.

The sodium hydroxide solution was mixed into the precursor slurry and immediately the foaming reaction, as described in Example 1, took place. The temperature of the reaction mass was maintained at about 220 F.- 230 F. After about 45 seconds, the foaming reaction was complete. The mixer was emptied and the product was screened. The product did not clog or blind the screens but, instead, was particulate and free flowing. The granules were tough and made excellent detergent tablets. The granules were noticeably less frangible than similar granules which did not contain the trisodium salts of nitrilotriacetic acid.

Example 5 Detergent slurries having the synthetic detergent compositions shown in the following table were prepared in exactly the same manner and utilized exactly the same components, with the exception of the synthetic detergents, as the slurry of Example 3. The results were substantially the same. The NTA'=H O deareated the precursor slurry. The precursor slurry was easily mixed and '4. The process of claim 3 wherein the final slurry contains about 2 moles of alkali metal hydroxide per mole of trimetaphosphate.

5. The process of claim 1 wherein the water-soluble salt of nitrilotriacetic acid is trisodium nitrilotriacetate.

SYNTHETIC DETERGENT COMPOSITION OF DETERGENT SLURRIES Detergent Components (Parts by Weight) Runs Anionic Paste (60% water, 15.5% sodium sulfate, 24.5%

active as listed below):

Sodium tallow alcohol sulfate-.-

Sodium alkyl benzene sulfonate (alkyl chain contains from 9-15 carbon atoms) Sodium tallow glyceryl ether sulfonate Olefin Sultanate- Sodium alkyl phenol ethylene oxide ether sulfate containing 8 units of ethylene oxide per molecule N onyl phenol containing 30 units of ethylene oxide per molecule 7 Dodecyl mercaptan containing 10 units of ethylene oxide per molec 7 Dinonylphenol containing units of ethylene oxide per mnlponlp Pluronic L64.

'IAE" (See Example 1)- What is claimed is: '1. A process for preparing detergent granules comprising the steps of i (1) forming a precursor slurry by mixing together, by

weight, based on the final slurry, from about to about of water, from about 0.2% to about 12% of a water-soluble salt of nitrilotriacetic acid, 5 to 30% of a detergent selected from the group consisting of soap, anionic synthetic non-soap detergents, nonionic synthetic deter-gents, switterionic synthetic detergents and mixtures thereof and from about 20% to about of an alkali-metal trimetaphosphate;

(2) adjusting the temperature of the precursor slurry between about F. and about 212 F.;

(3) admixing into the continuously stirred precursor slurry from about 1.5 to about 3.0 moles of an alkali metal hydroxide per mole of alkali metal trimetaphosphate to form the final slurry; said alkali metal hydroxide reacting with said trimetaphosphate and converting it to an alkali metal tripolyphosphate with a resulting evolution of a substantial amount of steam from the slurry, the temperature of the slurry 7 being maintained below about 275 F.

2. The process of claim 1 wherein the precursor slurry contains from about 2.0% to about 9.0% of the water+ soluble salt of nit-rilotriacetic acid by weight based on the final slurry.

3. The process of claim 2 wherein the final slurry contains from about 30% to about 38% water by weight based on the final slurry.

6. The process of claim 1 wherein the alkali metal hydroxide is sodium hydroxide and the alkali metal trimetaphosphate is sodium trimetaphosphate.

7. The process of claim 1 wherein the temperature of the precursor slurry is adjusted to between F. and F.

8. The process of claim 1 wherein the water-soluble salt of nitrilotriacetic acid is added to the precursor slurry before the addition of the alkali-metal trimetaphosphate to the precursor slurry.

9. In a process for making a detergent composition using a trimeta-phos-phate foamed process which comprises preparing a prec-ursorslurry containing water a detergent selected from .the group consisting of soap, anionic synthetic non-soap detergents, nonionic synthetic detergents, ampholytic synthetic detergents, zwitterionic synthetic detergents and mixtures thereof and alkali metal trimetaphosphate and adding thereto an alkali metal hydroxide to form a final slurry, the improvement which comprises adding to said precursor slurry from about .2% to about 12% of a water-soluble salt of nitrilotriacetic acid, by weight, based onthe final slurry, whereby the viscosity of the slurry is substantially decreased.

"' References Cited UNITED STATES PATENTS 3,303,134 2/1967 Shen 252-135 LEON D. ROSDOL, Primary Examiner.

S. E. DARD-EN, Assistant Examiner. 

1. A PROCESS FOR PREPARING DETERGENT GRANULES COMPRISING THE STEPS OF (1) FORMING A PRECUSOR SLURRY BY MIXING TOGETHER, BY WEIGHT, BASED ON THE FINAL SLURRY, FROM ABOUT 20% TO ABOUT 45% OF WATER, FROM ABOUT 0.2% TO ABOUT 12% OF A WATER-SOLUBLE SALT OF NITRILOTRIACETIC ACID, 5 TO 30% OF A DETERGENT SELECTED FROM THE GROUP CONSISTING OF SOAP, ANIONIC SYNTHETIC NON-SOAP DETERGENTS, NONIONIC SYNTHETIC DETERGENTS, SWITTERIONIC SYNTHETIC DETERGENTS AND MIXTURES THEREOF AND FROM ABOUT 20% TO ABOUT 60% OF AN ALKALI-METAL TRIMETAPHOSPHATE; (2) ADJUSTING THE TEMPERATURE OF THE PRECURSOR SLURRY BETWEEN ABOUT 140*F. AND ABOUT 212*F.; (3) ADMIXING INTO THE CONTINUOUSLY STIRRED PRECURSOR SLURRY FROM ABOUT 1.5 TO ABOUT 3.0 MILES OF AN ALKALI METAL HYDROXIDE PER MOLE OF ALKALI METAL TRIMETAPHOSPHATE TO FORM THE FINAL SLURRY; SAID ALKALI METAL HYDROXIDE REACTING WITH SAID TRIMETAPHOSPHATE AND CONVERTING IT TO AN ALKALI METAL TRIPOLYPHOSPHATE WITH A RESULTING EVOLUTION OF A SUBSTANTIAL AMOUNT OF STEAM FROM THE SLURRY, THE TEMPERATURE OF THE SLURRY BEING MAINTAINED BELOW ABOUT 275*F. 